defined as the amount of heat per unit mass absorbed or given off by the substance to change its temperature by one unit. It depends on the nature of the substance and its temperature. The SI unit of specific heat capacity is J kg – K – . If the amount of substance is specified in terms of moles µ , instead of mass m in kg, we can define heat capacity per mole of the substance by ( .
) where C is known as molar specific heat capacity of the substance. Like S , C also depends on the nature of the substance and its temperature. The SI unit of molar specific heat capacity is J mol – K – . However, in connection with specific heat capacity of gases, additional conditions may be needed to define C .
In this case, heat transfer can be achieved by keeping either pressure or volume constant. If the gas is held under constant pressure during the heat transfer, then it is called the molar specific heat capacity at constant pressure and is denoted by C p . On the other hand, if the volume of the gas is maintained during the heat transfer, then the corresponding molar specific heat capacity is called molar specific heat capacity at constant volume and is denoted by C v . For details see Chapter .
Table . lists measured specific heat capacity of some substances at atmospheric pressure and ordinary temperature while Table . lists molar specific heat capacities of some gases. From Table .
you can note that water has the highest specific heat capacity compared to other substances. For this reason water is also used as a coolant in automobile radiators, as well as, a heater in hot water bags. Owing to its high specific heat capacity, water warms up more slowly than land during summer, and consequently wind from the sea has a cooling effect. Now, you can tell why in desert areas, the earth surface warms up quickly during the day and cools quickly at night.
Table . Molar specific heat